Keypad

A keypad including;

• a plurality of keys for actuation by a user to input data into the keypad;
• a matrix electrical interconnection interconnecting the keys so that actuation of a key can be detected by scan signals applied to the matrix and by reading signals from the matrix electrical interconnection;
• control means for causing the matrix electrical interconnection to change state independently of the depression of a key to thereby disguise which of the keys has been pressed, and to interrogate the matrix electrical interconnection having regard to the caused change of state of the keys to determine which of the keys has actually been pressed;
• and
• state actuating means for causing the matrix interconnection to take up a predetermined state when a key is pressed to prevent the identity of the pressed key from being determined by an outside observer attempting to determine the duration of depression of the pressed key.

A keypad including;

• a plurality of keys for actuation by a user to input data into the keypad;
• a first switch and a second switch associated with each key, both of which switches undergo a change of state between an open and a closed condition when a respective key is actuated by the user;
• a common first electrical interconnection, interconnecting all of the first switches of the plurality of keys so that when any key is actuated a global signal is supplied to the common first electrical interconnection;
• a matrix electrical interconnection interconnecting the second switches of the plurality of keys so that actuation of a key can be detected by scan signals applied to the matrix for electrical interconnection and by reading signals from the matrix electrical interconnection;
• and
• a controller for detecting the global signal on the common first electrical interconnection and for supplying scan signals to the matrix electrical interconnection and reading signals from the matrix electrical interconnection to detect which key of the plurality of keys has been depressed.

A keypad including;

• a plurality of keys for actuation by a user to input data into the keypad;
• a switch associated with each key, which switch undergoes a change of state between an open and a closed condition when a respective key is actuated by the user;
• a matrix interconnection, interconnecting the switches, the matrix having pairs of lines interconnectable by the switches;
• state maintaining means for maintaining a t predetermined state of lines;
• and
• a controller for selectively changing the state of lines of the matrix and reading lines of the matrix to determine whether a key has been actuated, and wherein lines are maintained in a predetermined state by the state maintaining means notwithstanding the controller attempting to change the state of those lines.